That felt like looking for a needle in a haystack. We did find a viewlet that in its update method stored a portal tool on the viewlet, like so:def update(self): super(ViewletClass, self).update() self.workflow_tool = getToolByName(self.context, 'portal_workflow')After replacing that line, the messages went away after the next update. Might be that something else that went into that update caused it, but i thought i'd share my suspicion here in case anyone ever googles for this.